Show warning for x32 game on x64 os

src/debug.cpp

@@ -1728,16 +1728,28 @@ std::string game_info::operating_system_version()
 #endif
 }
 
-std::string game_info::bitness()
+std::optional<int> game_info::bitness()
 {
     if( sizeof( void * ) == 8 ) {
-        return "64-bit";
+        return 64;
     }
 
     if( sizeof( void * ) == 4 ) {
-        return "32-bit";
+        return 32;
     }
 
+    return std::nullopt;
+}
+
+std::string game_info::bitness_string()
+{
+    auto b = bitness();
+    if( b && *b == 32 ) {
+        return "32-bit";
+    }
+    if( b && *b == 64 ) {
+        return "64-bit";
+    }
     return "Unknown";
 }
 
@@ -1799,7 +1811,7 @@ std::string game_info::game_report()
     report <<
            "- OS: " << operating_system() << "\n" <<
            "    - OS Version: " << os_version << "\n" <<
-           "- Game Version: " << game_version() << " [" << bitness() << "]\n" <<
+           "- Game Version: " << game_version() << " [" << bitness_string() << "]\n" <<
            "- Graphics Version: " << graphics_version() << "\n" <<
            "- LAPI Version: " << cata::get_lapi_version_string() << "\n" <<
            "- Game Language: " << lang_translated << " [" << lang << "]\n" <<
@@ -1808,4 +1820,38 @@ std::string game_info::game_report()
     return report.str();
 }
 
-// vim:tw=72:sw=4:fdm=marker:fdl=0:
+std::optional<int> get_os_bitness()
+{
+#if defined(_WIN32)
+    SYSTEM_INFO si;
+    GetNativeSystemInfo( &si );
+    switch( si.wProcessorArchitecture ) {
+        case PROCESSOR_ARCHITECTURE_AMD64:
+            return 64;
+
+        case PROCESSOR_ARCHITECTURE_INTEL:
+            return 32;
+
+        default:
+            // FIXME: other architectures?
+            break;
+    }
+#elif defined(__linux__)
+    std::string output;
+    output = shell_exec( "getconf LONG_BIT" );
+
+    if( !output.empty() ) {
+        // remove trailing '\n', if any.
+        output.erase( std::remove( output.begin(), output.end(), '\n' ),
+                      output.end() );
+    }
+
+    if( output == "64" ) {
+        return 64;
+    } else if( output == "32" ) {
+        return 32;
+    }
+#endif
+    // FIXME: osx, android
+    return std::nullopt;
+}

src/debug.h

@@ -48,6 +48,7 @@
 // Includes                                                         {{{1
 // ---------------------------------------------------------------------
 #include <iostream>
+#include <optional>
 #include <string>
 #include <type_traits>
 #include <utility>
@@ -110,9 +111,12 @@ std::string operating_system();
 /** Return a detailed version of the operating system; e.g. "Ubuntu 18.04" or "(Windows) 10 1809".
  */
 std::string operating_system_version();
-/** Return the "bitness" of the game (not necessarily of the operating system); either: 64-bit, 32-bit or Unknown.
+/** Return the "bitness" of the game (not necessarily of the operating system); either: 64, 32 or nullopt.
  */
-std::string bitness();
+std::optional<int> bitness();
+/** Return the "bitness" string of the game (not necessarily of the operating system); either: 64-bit, 32-bit or Unknown.
+ */
+std::string bitness_string();
 /** Return the game version, as in the entry screen.
  */
 std::string game_version();
@@ -240,6 +244,11 @@ std::string capture_debugmsg_during( const std::function<void()> &func );
  */
 void replay_buffered_debugmsg_prompts();
 
+/**
+ * Retrieves OS bitness (32, 64 or nullopt if detection failed)
+ */
+std::optional<int> get_os_bitness();
+
 // Debug Only                                                       {{{1
 // ---------------------------------------------------------------------
 

src/main_menu.cpp

@@ -604,6 +604,21 @@ bool main_menu::opening_screen()
         return false;
     }
 
+    std::optional<int> os_bitness = get_os_bitness();
+    std::optional<int> game_bitness = game_info::bitness();
+    if( os_bitness && *os_bitness == 64 && game_bitness && *game_bitness == 32 ) {
+        popup( _(
+                   "You are running x32 build of the game on a x64 operating system.  "
+                   "This means the game will NOT be able to access all memory, "
+                   "and you may experience random out-of-memory crashes.  "
+                   "Consider obtaining a x64 build of the game to avoid that, "
+                   "but if you *really* want to be running x32 build of the game "
+                   "for some reason (or don't have a choice), you may want to lower "
+                   "your memory usage by disabling tileset, soundpack and mods "
+                   "and increasing autosave frequency."
+               ) );
+    }
+
     load_char_templates();
 
     ctxt.register_cardinal();